The present invention concerns an implantable infusion pump, and in particular, an implantable infusion pump as well as independent components therefor that enable securing the pump within a living body, multi-stage filtration, and protection of a fluid-delivery catheter in and about the pump housing while improving volumetric efficiency of the pump configuration.
The present invention relates to an implantable infusion pump for infusing drugs or other chemicals or solutions into a body wherein the infusion pump is implanted. Further, in at least one embodiment, the present invention relates to an implantable infusion pump that compensates for changes in both ambient pressure and ambient temperature so as to accurately control the flow rate of infusates from the implantable infusion pump into the body.
Infusion pump designs were rarely seen in medical literature until the 1950s. Most of these early infusion pumps were extracorporeal devices of various designs. One such device included a reciprocating air pump driven by an electric motor. Yet another design considered comprised a metal housing for a glass syringe and a compression chamber fed by a tank of nitrogen gas. Yet another such infusion pump included a motorized syringe pump which included an electric motor connected to the worm drive that moved a syringe plunger by a gear box. The gears were interchangeable such that replacement of the gears permitted different delivery rates. Yet another infusion pump included a syringe plunger driven by a rider on a threaded shaft. While this is but a sampling of such devices, it should be appreciated that numerous other designs were considered and used for extracorporeal infusion devices.
Modern constant-flow implantable infusion devices, or implantable pumps, for delivering an infusate (e.g., medicaments, insulin, etc.) commonly have a rigid housing that maintains a collapsible infusate reservoir. The housing includes a needle-penetrable septum that covers a reservoir inlet. A flow passage is provided between the reservoir and an exterior surface of the device, such flow passage includes, or defines, a restrictor to establish a maximum output infusate flow rate. At the flow passage outlet, a flexible delivery catheter is provided.
Practically, such a device is implanted at a selected location in a body so that (i) the inlet septum is proximate to the patient""s skin and (ii) a distal end of the catheter is positioned at a selected delivery site. Infusate can then be delivered to the infusion site by forcing such fluid from the device reservoir. When the infusate reservoir becomes empty, the reservoir is refillable through the septum inlet by injecting a new supply of infusate through the apparatus"" inlet septum. Due to the location of the device in relation to the skin of the patient, injection can be readily accomplished using a hypodermic needle (or cannula).
Infusate is expelled from the reservoir to an infusion site by collapsing the reservoir. While some infusion pumps use an electrically powered mechanism to force infusate from the reservoir, other such devices commonly use a two-phase fluid, or propellant, that is contained within the rigid housing and is further confined within a fluid-tight space adjacent to the infusate reservoir.
The propellant is both a liquid and a vapor at patient physiological temperatures, e.g., 98.6xc2x0 F., and theoretically exerts a positive, constant pressure over a full volume change of the reservoir, thus effecting the delivery of a constant flow of infusate. More particularly, when the infusate reservoir is expanded upon being refilled, the propellant is compressed, where a portion of such vapor reverts to its liquid phase and thereby recharges the vapor pressure power source of the pump. The construction and operation of implantable infusion pumps of this type are described in detail, for example, in U.S. Pat. Nos. 3,731,681 and 3,951,147.
Gas-driven infusion pumps typically provide a cost-effective means to deliver a consistent flow of infusate throughout a delivery cycle. Notwithstanding, the rigid housing of the gas-driven infusion pump allows both environmental temperature and atmospheric pressure to affect an output fluid flow. With some drugs, particularly those having small therapeutic indices, such changes in drug infusion rates are undesirable and, in certain situations, unacceptable.
Circumstances readily exist where either environmental temperature or pressure can rapidly change a significant amount. For example, in regard to temperature, an internalized pump pressure can change as much as 0.5 psi for each 1xc2x0 F. change in body temperature. Thus, for example, assuming a pump driving force of 8 psi at 98.6xc2x0 F., a twenty-five percent (25%) increase in pressure and drug flow rate can result from a fever of only 102.6xc2x0 F.
An even more serious situation results from changes in atmospheric pressure. Although minor variations in atmospheric pressure at any given location on earth does not significantly affect delivery flow rates, with modern modes of transportation, a patient can rapidly change altitude during travel, such as when traveling in the mountains or when traveling by plane.
Again, the rigid housing of the conventional, gas-driven infusion pump is intended to produce a constant internal pressure (at constant temperature) independent of the external pressure. Largely due to compliance by the lungs and venous circulatory system, hydrostatic pressure within the human body closely follows atmospheric pressure. The net effect is a pressure differential across the fluid flow restrictor of infusion pump (typically a capillary tube or the like) which changes linearly with external pressure. Consequently, a delivered infusate flow rate can increase as much as forty percent (40%) when a patient takes a common commercial airline flight.
A viable solution to address changes in atmospheric conditions for constant-flow infusion pumps is disclosed in U.S. Pat. No. 4,772,263, herein incorporated by reference in its entirety. Specifically, in place of the conventional rigid enclosure that maintains a two-phase fluid, the disclosure teaches forming the fluid reservoir between a rigid portion (which maintains at least the inlet septum and the restrictor) and a flexible drive-spring diaphragm. The diaphragm is exposed to the body of the patient and xe2x80x9csensesxe2x80x9d internal body pressure so as to compensate for changes in the internal body pressure caused by changes in atmospheric pressure and temperature.
While the disclosure of U.S. Pat. No. 4,772,263 provides a foundational description for a pump having a drive-spring diaphragm capable of constant-flow delivery, such patent does not fully consider alternatives for restrictor and/or flow passage outlet placement that may provide for a safer practical configuration as well as capitalize on the unique structure of the drive-spring diaphragm.
Moreover, U.S. Pat. No. 4,772,263 is silent to a means to incorporate a conventional bolus port with its unique drive-spring diaphragm design. A bolus port enables direct infusion of a fluid through the delivery catheter. A bolus port is typically a separate septum that is in fluid communication with an outlet of an associated infusion pump and a delivery catheter therefor. Typically, certain one-way valving structures can prevent fluid that is injected through the bolus port from-flowing upstream to the infusate reservoir of the infusion pump.
The present invention relates to an infusion pump for implantation in a living body. The infusion pump includes a housing having a fluid chamber, wherein the housing includes a spring-energy source for driving an infusate (e.g., medicaments, insulin, etc.) out of the fluid chamber and compensating for changes in internal body pressure and/or internal body temperature. The housing further includes an inlet conduit in communication with the fluid chamber and an outlet conduit in communication with the fluid chamber that leads to an infusion site in the body. A self-sealing, penetrable member is provided in the inlet conduit to facilitate periodic refilling of the drug chamber when the infusion pump is implanted. The spring-energy source allows a pressure differential between the fluid chamber and the internal body pressure to remain constant and unaffected by changes in body temperature or atmospheric pressure.
In accordance with one aspect of the present invention, the ""spring-energy source is a spring diaphragm that forms a flexible, exterior rear wall of the fluid chamber that operatively applies pressure on a fluid solution stored in the fluid chamber equivalent to a predetermined constant force collectively exerted by the spring diaphragm and an internal body pressure of the patient.
In accordance with another aspect of the present invention, an infusion pump for implantation in a living body has a variable-volume fluid chamber, a housing, and a driving spring. An inlet conduit of the pump includes a self-sealing penetrable member and extends between a surface of the housing and the fluid chamber. An outlet conduit of the pump communicates with the fluid chamber and is connectable to a delivery catheter. In addition to the driving spring being adapted to supply a principle force to drive a fluid stored in the fluid chamber into the body, the driving spring also includes the outlet conduit, which enters, passes through, and exits the driving spring.
Another aspect of the present invention is directed to an implantable pump having a housing, an outlet conduit, and a multi-stage filter system. The housing defines a variable-volume fluid chamber to store infusate. The outlet conduit is in communication with the fluid chamber and connectable to a delivery catheter. The multi-stage filter system, positioned within the outlet conduit, filters infusate prior to delivery via the delivery catheter.
Another aspect of the present invention is directed to an implantable pump that includes a housing having both a collapsible fluid chamber to store infusate and an energy source to collapse the fluid chamber. The pump further includes an inlet conduit and an outlet conduit. The inlet conduit, having a self-sealing penetrable member positioned therein, is located at a first position relative to the housing and in communication with the fluid chamber. The outlet conduit is in communication with the fluid chamber and connectable to a delivery catheter. The pump further includes a member having (i) a first mating surface to receive the housing and (ii) a reinforced-elastomer suture structure, extending substantially about a perimeter of the member, to receive and maintain applied sutures to secure the pump within a living body.
Another aspect of the present invention is directed to an implantable pump that includes a bolus port and a housing having a collapsible fluid chamber to store infusate and an energy source to collapse the fluid chamber. The pump further includes an inlet conduit and an outlet conduit. The inlet conduit, having a self-sealing penetrable member positioned therein, is located at a first position relative to the housing and in communication with the fluid chamber. The outlet conduit is in communication with the fluid chamber. The pump further includes a member having (i) a first mating surface to receive the housing and (ii) a bolus port receptacle, having an inlet and an outlet, to receive the bolus port, wherein the outlet is connectable to a delivery catheter. A connection conduit operatively couples the inlet of the bolus port receptacle and the outlet conduit.
An object of the present invention is to provide an implantable infusion pump having an outlet flow passage that is protected by the upper housing and is removed from potential damage during a refill operation.
Another object of the present invention is to provide an implantable infusion pump having a drive-spring diaphragm with an outlet flow passage that passes through the drive-spring diaphragm.
Another object of the present invention is to provide a suture structure that receives and is attachable to an infusion pump, wherein this structure enables a received infusion pump to be conveniently secured at an implantation site.
Another object of the present invention is to provide a structure that receives and is attachable to an infusion pump and that facilitates a fluid connection between the infusion pump and a bolus port.
Another object of the present invention is to provide a two-stage filtration system for an implantable infusion pump, wherein a first stage functions to filter micro-emboli and a second stage functions to filter greater particulate matter.